Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CA 02390764 2002-07-17
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Description
TRUSS STYLE STICK OR BOOM
Technical Field
This invention relates to a work machine, such as an excavator,
backhoe, front shovel or material handler, more particularly to the structure
of a
stick and/or boom for use with the work machine.
Back or~und
In a typical arrangement, the boom and stick have an enclosed,
box like configuration. For example, U.S. Patent No. 3,220,578 discloses a
stick
having an enclosed, box-like shape.
Structural members for work machines such as backhoes,
excavators and front shovels typically include a boom pivotally attached to a
machine frame at a first end, a stick pivotally attached to the boom at a
second
end and a bucket or material handling device further attached to the stick.
Drive
mechanisms, often hydraulic cylinders, are coupled to the machine in manner
that
moves the boom relative to the machine frame, the stick relative to the boom
and
the material handler relative to the stick.
In order to achieve the desired movement of structural members,
sticks and booms are typically have three pivot (attachment) points. Two of
the
three pivot points are typically disposed at the first and second end,
respectively,
of the boom or stick. The first and second pivot points typically define a
first
longitudinal axis. The third pivot point is typically disposed at a
predetermined
distance from the first longitudinal axis. A second axis can be defined by
extending a line from the first pivot point to the offset pivot point and a
third axis
can be defined by extending a line from the second pivot point to the offset
pivot
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point. The first longitudinal axis, the second axis and the third axis form a
triangle.
A problem with the box-like configuration is that such a structure
is high in cost to manufacture and heavy in weight. When the boom or stick is
S unnecessarily heavy, the amount of material such as dirt or rock that can be
carried by a bucket is reduced, thus requiring extra bucket loads to fill a
truck.
The additional weight also induces additional stress into other components of
the
work machine; this may adversely effect the life of the work machine. The
power requirements to lift or move the additional weight increases the engine
and
related component size, resulting in increased machine cost. Unnecessary
weight, generally, reduces efficiency and increases operating costs of the
machine.
The present invention is directed toward overcoming one or more
of the problems set forth above.
1 S Summary of the Invention
In an embodiment of the present invention, a work machine
having at least one of a boom and a stick. A material-handling device is
attached
to the boom or stick. The boom or stick being constructed of a box portion and
an attached truss portion.
In another embodiment of the present invention, a structural
member for a work machine is disclosed. The structural member has a first end
and a second end, a first pivot point disposed adjacent the first end and a
second
pivot point is disposed adjacent the second end. The structural member
comprises an offset pivot point having a plurality of longitudinal members
extending to the box section, forming a rigid structure.
In yet another embodiment of the present invention, a method of
reducing the weight in one of a stick and boom of a work machine. The method
includes constructing a box portion having a first pivot point, a second pivot
point and a first longitudinal axis extending therethrough. A truss portion is
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constructed having a plurality of longitudinal members intersecting a third
pivot
point. Attaching the truss section to the box section completes the stick or
boom.
Brief Description of the Drawinys_
FIG. 1 is a perspective view of a portion of a work machine,
according to one aspect of the present invention.
FIG. 2 is a side view of a boom of a work machine, according to
another aspect of the present invention.
Detailed Description
Referring to FIG. 1, a work machine 10 includes a boom 12, a
stick 14 and a material-handling device 16. In this application an excavator
is
used to define the work machine 10, the material handling device 16 is a
bucket
18. However, the invention may be applied to other types of work machines,
such as a wheel loader, backhoe, or telescopic material handler. In the case
of a
wheel loader, one material-handling device could have a mechanism for grasping
the material, such as a grapple. The stick 14 is pivotally connected to the
boom
12 at stick pivot point 20 and the bucket 18 is pivotally connected the stick
14 at
bucket pivot point 22.
According to one aspect of the present invention, the stick 14
includes a first portion (box portion) 24 that is constructed from a plurality
of
plate sections attached to one another to create a box or rectangular cross-
section.
The box portion 24 is substantially enclosed around its periphery, as
illustrated in
FIG. 1. According to this embodiment, the truss portion 26 includes a pair of
triangular truss members 28 that are spaced apart from each other and
interconnected by cross members 30. The truss portion 26 is pivotally
connected
to the box portion 24 at base pivot point 32 so that it is free to rotate with
respect
to the box portion 24. More specifically, a base plate 34 is secured to the
box
portion 24 and the truss portion 26 is pivotally attached to the base plate 34
at
base pivot point 32. However, it is important that the truss portion 26 be
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CA 02390764 2002-07-17
generally fixed in relation to the box portion 24. Therefore, a pair of
support
members 36 extend from the end of the truss portion 26 to the box portion 24
to
prevent the truss portion 26 from rotating with respect to the box portion 24
about
pivot point 32. As a result of this arrangement, the truss portion 26 is able
to
withstand forces created during operation of the machine. However, it should
be
understood that the invention is not limited to having the truss portion 26
pivotally secured to the base portion 26. One suitable alternative would be to
have the truss portion 26 solidly attached to the box portion 24. Another
alternative is to mount the truss portion 26 using the current stick 14 to
boom 12
connecting pin 20.
It should be noted that the base plate 34 may either be integrally
secured to the box portion 24 or, alternatively, the base plate 34 may be
removably attached using bolts, screws, or the like. Further, it should be
understood that this is just one example of a suitable truss portion 26 and
the
invention is not limited to any particular truss design.
A first drive mechanism 38 is provided for pivoting the stick 14
with respect to the boom 12. A second drive mechanism 40 is provided for
pivoting the bucket 18 or material handling device 16 with respect to the
stick 14.
A third drive mechanism (not shown) is provided for pivoting the boom 12 with
respect to a machine frame. In this application, a typical drive mechanism
includes a hydraulic cylinder 44 and rod 46. A number of drive mechanisms may
be used in place of the cylinder 44 and rod 46, including cables and pulleys.
With respect to the first drive mechanism 38, the base end of the
cylinder 44 is pivotally connected to the boom 12 at pivot point 48 and distal
end
of the rod 46 is pivotally attached to the truss portion 26 at a first truss
pivot point
50. With respect to the second drive mechanism 40, a base end 52 of the
cylinder
44 is pivotally connected to the truss portion 26 at a second truss pivot 54
and the
distal end of the rod 46 is pivotally connected to a linkage 56 at a linkage
pivot
point 58. The linkage 56 includes a first pair of link members 60 which are
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pivotally connected at one end to the distal end of the rod 46 at the first
linkage
pivot point 58 and at the other end to the stick 14 at a second linkage pivot
point
62. The linkage further includes a second pair of link members 64 which are
connected at one end to the first linkage pivot point 58 and at the opposite
end to
a back of the bucket 18 at a third linkage pivot point 66. The linkage and
drive
mechanisms are conventional and the invention is not intended to be limited to
any particular linkage or drive mechanism.
According to another aspect of the invention, the boom 12' may
included a truss portion 26' in combination with a box portion 24'. More
specifically and with reference to FIG. 2, the boom 12' may include the first
portion (box portion) 24' and the second portion (truss portion) 26'. The
truss
portion 26' includes a first pair of truss members 70, 72 which, together with
the
box portion 24' forms a triangle. Although not shown, a second pair of truss
members may be laterally spaced from the first pair of truss members 70, 72,
and
suitably interconnected by one or more connecting members, as with the truss
portion 22 discussed in regard to the stick 14.
The boom 12' is pivotally attached to the machine 10 and the stick
14' is pivotally attached to the boom 12'. More specifically, a first end 74
of the
boom 12 includes a boom pivot point 76 for pivotally attaching the boom 12 to
a
machine frame 78. Correspondingly, a second end 80 of the boom 12 includes
the stick pivot point 18' for pivotally attaching the stick 14 to the boom 12.
The
truss portion 16' includes the pivot point 48' for attaching the first drive
mechanism 36'. The first drive mechanism 36' fiuther attaches to a stick.
Industrial Applicability
In operation, the apparatus of the present invention operates in a
conventional manner. For example, the first drive mechanism 38 is operable to
pivot to stick 14 with respect to the boom 12. The second drive mechanism 40
is
operable to pivot the bucket 18 or material handling device 16 with respect to
the
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stick 14 and the third drive mechanism 42 is operable to pivot the boom with
respect to the machine frame (not shown).
The present invention provides a stick 14 and boom 12 that is
constructed with less steel, therefore reducing the weight and cost of the
structure. The reduced structure weight additionally increases the amount of
material that the bucket 18 can lift. Fuel efficiency is also improved due to
the
reduced weight, because the machine is not required to move the excess weight.
In some cases, the amount of weight reduction of the structure may increase
payload capacity enough to reduce the horsepower requirement for the engine,
allowing the use of a lower cost engine. In other cases the increase payload
capacity may permit use of a smaller machine, saving the customer some capital
expense.
In addition, it is possible to have a variety of truss designs adapted
to fit different machine configurations. A single machine may be reconfigured
for different functions by changing the material handling device 20, the stick
14
or the boom 16.
It should be understood that while one embodiment is described in
connection with an excavator, the present invention if readily adapted to
provide
similar functions for other work machines. Other aspects, objects and
advantages
of the present invention can be obtained from a study of the drawings, the
disclosure and the appended claims.
